8B.4
Future Climate of the North Pacific as Projected by IPCC-AR4 Models
Muyin Wang, University of Washington, Seattle,, WA; and J. E. Overland
Major shifts in species distribution and abundance in North Pacific marine ecosystems are expected in the first half of the 21st century due to climate change, from corals in the south to walrus and polar bears in the north. The results of the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC-AR4), and availability of the individual IPCC model simulations, provide a major opportunity to assess the magnitude and patterns of climate change for the North Pacific. In this study we evaluate simulations from 23 models of climate patterns such as the Pacific Decadal Oscillation (PDO), sea surface temperature (SST), and sea ice coverage, by comparing them with 20th century observations. After careful evaluation of the models based on bias and variance criteria, “outlier” models are removed from the ensembles and projections for the next 50 years are made based on the remaining sub-set of models. Results from a sub-group of 10 models which simulate the spatial pattern and spectra of the twentieth-century SST (PDO) well, show that projected SST increases will exceed the range of natural variability in 30-50 years over most of the North Pacific. Projections of sea-ice area over the Sea of Okhotsk and Bering Sea by a sub-group of seven models show a reduction of winter sea ice of 40% by 2050. We find a deepening of the Aleutian low in winter and an increase in North Pacific sea level pressure in summer. Greenhouse gas emission scenarios diverge after 2050, and the possibility of more complex feedbacks increase, thus we have less confidence in longer range projections.
Session 8B, Climate Prediction
Tuesday, 22 January 2008, 3:30 PM-5:30 PM, 217-218
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